Technique and System for Intervening in a Wellbore Using Multiple Reels of Coiled Tubing

ABSTRACT

A method that is usable with a well includes changing a connection between a first coiled tubing segment and a second coiled tubing segment while an upper end of the first coiled tubing section is out of the well and a portion of the first coiled tubing segment is deployed in the well. After the connection is changed, the method includes deploying the remainder of the first coiled tubing segment into the well or retrieving the portion of the first coiled tubing segment from the well.

This application is a continuation-in-part of U.S. patent application Ser. No. 11/115,610, entitled, “TUBING CONNECTOR,” which was filed on Apr. 27, 2005, and is hereby incorporated by reference in its entirety.

BACKGROUND

The invention generally relates to a technique and system for intervening in a wellbore using multiple reels of coiled tubing.

Coiled tubing is used in a broad array of applications in oilfield operations such as drilling and completing oil and gas wells, conveying equipment, and performing maintenance on completed oil and gas wells. To deploy coiled tubing into a wellbore, the coiled tubing string is unreeled or unspooled from a coiled tubing reel, run over an injector gooseneck and inserted into a wellhead system for injecting the coiled tubing into the wellbore. To retract coiled tubing from a wellbore, the coiled tubing is reeled or spooled back out of the wellbore through the wellhead system over the gooseneck and onto the coiled tubing reel. It is known that bending and straightening the coiled tubing in well site operations and spooling the coiled tubing on a reel causes low cycle fatigue in the coiled tubing, which if left unchecked can lead to failure of the coiled tubing. The ability to unreel and reel coiled tubing as a continuous tubing string nevertheless offers attractive operational advantages over jointed pipe that requires connections at each relatively short length of pipe.

It is not uncommon for the reel to contain ten thousand feet or more of coiled tubing, as the length of the tubing on the reel typically is a function of the deepest intervention in which the coiled tubing will be used. Furthermore, additional coiled tubing typically is added to the reel for purposes of creating spare tubing that may be cut off to remove a damaged section.

Challenges typically arise in transporting the reel to the well site and handling the coiled tubing reel at the well site due to the size of the reel. Thus, there is a continuing need for better ways to deploy a coiled tubing string into a well and retrieve the string from the well.

SUMMARY

In an embodiment of the invention, a method that is usable with a well includes changing a connection between a first coiled tubing segment and a second coiled tubing segment while an upper end of the first coiled tubing segment is out of the well and a portion of the first coiled tubing segment is deployed in the well. After the connection is changed, the method includes deploying the remainder of the first coiled tubing segment into the well or retrieving the portion of the first coiled tubing segment from the well.

In another embodiment of the invention, a system that is usable with a well includes a first coiled tubing segment, a second coiled tubing segment and slips. The slips secure an upper end of the first coiled tubing segment when the first coiled tubing segment is partially deployed in the well to permit the second coiled tubing segment to be selectively connected to or disconnected from the first coiled tubing segment.

In another embodiment of the invention, a method of deploying coiled tubing in a wellbore includes providing a coiled tubing connector having a body with a longitudinal bore therethrough, the body including a first end section and a second end section sections. Each end section includes a tapered external surface and a stiff section disposed between the first and the second end sections. The method also includes disposing the first end section within a first coiled tubing having a wall thickness and disposing the second end section within a second coiled tubing having a wall thickness different than the wall thickness of the first coiled tubing. The method further includes securing the stiff section to the inner diameter of each of the first and second coiled tubings, thereby forming a connected tubing and lowering the connected tubing into a wellbore.

Advantages and other features of the invention will become apparent from the detailed description, drawing and claims.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram of a well according to an embodiment of the invention.

FIG. 2 is a flow diagram depicting a technique to deploy coiled tubing in a well according to an embodiment of the invention.

FIG. 3 is side view of a specific embodiment of a coiled tubing connector according to an embodiment of the invention, and in use to connect a section of coiled tubing to a tool string.

FIG. 4A is a side view of another specific embodiment of a coiled tubing connector according to an embodiment of the invention similar to the one shown in FIG. 3 but shown not connected to any coiled tubings.

FIG. 4B is a side view of another specific embodiment of a coiled tubing connector according to an embodiment of the invention.

FIG. 4C is a side view of another specific embodiment of a coiled tubing connector according to an embodiment of the invention.

FIG. 5 is side view of two coiled tubing connectors according to an embodiment of the invention, and in use to connect coiled tubing to a tool string.

FIG. 6 is a side view of a specific embodiment of a coiled tubing connector according to an embodiment of the invention, and in use to connect two sections of coiled tubing to a tool string.

FIG. 7A is a strain diagram from a finite element model of a prior art internal coiled tubing connector having a flexible center section.

FIG. 7B is a strain diagram from a finite element model of an embodiment of a coiled tubing connector according to an embodiment of the invention.

FIG. 8 is side view of another specific embodiment of a coiled tubing connector according to an embodiment of the invention, and in use to connect two sections of coiled tubing.

FIGS. 9, 10 and 11 are side views of specific embodiments of a coiled tubing connector according to other embodiments of the invention and in use to connect a section of coiled tubing to a tool string.

FIG. 12 is a schematic diagram illustrating a two piece coiled tubing connector according to another embodiment of the invention.

DETAILED DESCRIPTION

Referring to FIG. 1, an embodiment 10 of a well in accordance with the invention includes a wellbore 20, which may or may not be cased by a casing string 22. During the drilling, completion and maintenance of the well 10, a coiled tubing string 30 may be run into the wellbore 20 to perform a specific function, and thereafter, the coiled tubing string 30 may be retrieved from the wellbore 20. As a more specific example, to treat the well 10, the coiled tubing string 30 may be run downhole inside the wellbore 20 for purposes of introducing a stimulation fluid.

Unlike conventional arrangements, the coiled tubing string 30 is formed from relatively short, connected coiled tubing segments (segments of approximately 2000, 3000, 4000 or 5000 feet, as examples) instead of, for example, one relatively long continuous segment (a segment of 10,000 feet or more, for example) that spans the length of the intervention. To accomplish this, the coiled tubing is transported to the well in several reels 35 (one of which is depicted in FIG. 1), each of which may contain one of the coiled tubing segments. Each coiled tubing segment that forms the coiled tubing string 30 may be a continuous length of coiled tubing, and connectors are used to concatenate the coiled tubing segments together for purposes of forming the string 30. As further described below, the coiled tubing string 30 may contain tools that may be added at the end of the string 30 as well at intermediate locations of the string 30 due to the string's segmented design.

In accordance with embodiments of the invention, each coiled tubing segment is transported to the well site on its own reel 35 and may have an attached connector at each end, which is constructed to mate with a connector of another coiled tubing segment or tool. Thus, in these embodiments of the invention, a two piece connector assembly (such as one female connector and one male connector) is used to join coiled tubing segments and add tools to the coiled tubing string 30. In other embodiments of the invention, a one piece connector assembly may be used to connect coiled tubing segments and add tools to another segment or tool. Many variations are therefore contemplated and are considered to be within the scope of the appended claims.

As a more specific example, in accordance with some embodiments of the invention, one end of the coiled tubing segment may have a female connector, and the other end of the coiled tubing segment may have a male connector. Thus, to join two coiled tubing segments together, the male and female connectors from the segments are mated together. FIG. 1 depicts two exemplary coiled tubing segments in connection with the deployment or retrieval of the coiled tubing string 30 to/from the well 10: an upper coiled tubing segment 30 a that is located outside of the wellbore 20 and is partially wound around its associated reel 35; and a lower coiled tubing segment 30 b that has previously been unwound from its associated reel (not shown), is partially disposed in the wellbore 20 and is connected at its lower end to another coiled tubing segment or tool. The upper coiled tubing segment 30 a is attached at its lower end via its connector 70 to a mating connector 80, which, in turn, is connected to the upper end of the lower coiled tubing section 30 b.

For the state of the well 10 depicted in FIG. 1, the upper end of the lower coiled tubing segment 30 b is engaged by slips 56, which secure the upper end so that the connector 80 may be connected to or disconnected from the connector 70, depending on whether the coiled tubing string 30 is being deployed in or retrieved from the wellbore 20.

The upper coiled tubing segment 30 a is partially wound around its associated reel 35 and extends through a coiled tubing injector 50 and a gooseneck 40. On the reel 35, the end of the coiled tubing segment 30 a is secured to an end connector 88 that is mated to a connector 78 that, in turn, is secured to a shorter coiled tubing segment 30 c, which is mounted to the drum of the reel 35. The shorter coiled tubing segment 30 c has a length that is sufficient to extend over the gooseneck 40 and the injector 50 to the position where the end connector 88 is secured by the slips 56. Thus, when the coiled tubing segment 30 a is deployed, the coiled tubing segment 30 c unwinds from the reel 35 until the connectors 78 and 88 pass through the injector 50, and the upper end of the coiled tubing segment 30 a is secured by the slips 56. At this point, the connectors 78 and 88 are disconnected, the shorter coiled tubing segment 30 c is wound back on the reel 35, the reel 35 containing the shorter coiled tubing segment 30 c is removed; and subsequently, a coiled tubing segment (from another reel) may be unwound and run through the injector 56 and attached to the coiled tubing segment 30 a in a similar manner. More coiled tubing segments may be added to the coiled tubing string 30 in a similar manner. The opposite process occurs for retrieving the coiled tubing string 30 from the well.

In accordance with some embodiments of the invention, the connectors 70 and 78 may be female connectors, and the connectors 80 and 88 may be male connectors.

To summarize, in accordance with some embodiments of the invention, a technique 100 (see FIG. 2) to deploy coiled tubing in a well includes deploying (block 104) the next coiled tubing segment through the injector 50 and into the wellbore 22. If a determination is made (block 108) that another coiled tubing segment is to be deployed, then the upper end of the uppermost partially deployed coiled tubing segment is secured (block 112) by the slips 56 so that the lower end of the next coiled tubing segment to be deployed is attached to the uppermost deployed coiled tubing segment, pursuant to block 114. The technique 100 continues with block 104 to deploy the next coiled tubing segment so that the blocks 104, 108 and 112 are repeated for each coiled tubing segment.

The coiled tubing string 30 may likewise be retrieved from the well in segments by a process that includes, for each coiled tubing segment that emerges from the well, engaging the upper end of the coiled tubing segment with slips, disconnecting the coiled tubing section from the coiled tubing section above, connected the coiled tubing section to a shorter coiled tubing section that is connected to the drum of a reel and then, winding the shorter coiled tubing section and now attached coiled tubing section from the well back onto the reel. This process continues until all coiled tubing segments have been wound onto their respective reels and thus, the coiled tubing string 30 has been retrieved from the wellbore 20.

As depicted in FIG. 1, among its other features, the well 10 may include a well tree 31 through which the coiled tubing string 30 passes and which seals off the region of the string 30 above the tree from the wellbore 20. The well tree 31 may include, as examples, a lubricator and a blow out preventer (BOP) and may include ports to communicate fluids to and from the wellbore 20.

In addition to including coiled tubing sections, the coiled tubing string 30 may include various tools, depending on the particular embodiment of the invention. In this regard, the coiled tubing string 30 may include, for example, a bottom hole assembly (BHA) (not shown in FIG. 1), which is attached to the bottom end of the coiled tubing string 30 and thus, is attached to the bottom end of the first coiled tubing segment that is deployed into the wellbore 20. Because the coiled tubing string 30 is formed from multiple segments, a tool may also be incorporated into the coiled tubing string 30 at an intermediate position above the bottom end of the string 30. In this regard, as depicted in FIG. 1, in accordance with some embodiments of the invention, a tool 60 may be disposed between the upper and lower ends of the coiled tubing string 30 for purposes of performing a particular function relating to the job being performed by the coiled tubing string 30.

For example, the tool 60 may be a swabbing tool for purposes of preventing a fluid that is injected via the coiled tubing string 30 at its lower end from reaching an upper section of the wellbore 20. In this regard, the swabbing tool 60 may form an annular barrier around the exterior of the coiled tubing string 30 at a particular intermediate location of the coiled tubing string 30. Thus, for example, if a particular zone of the well below the swabbing tool 60 is being treated with a stimulation fluid, the tool 60 prevents the stimulation fluid from reaching the region of the well above the tool 60, where damage may possibly occur.

As another example, a tool that is deployed on the coiled tubing string 30 may include one or more sensors for purposes of detecting when a particular fluid, such as a stimulation fluid, has reached the tool. In this regard, an operator at the surface of the well may monitor results that are communicated uphole from the tool for purposes of determining when to halt pumping of treatment fluid into the well via the coiled tubing string 30. Other tools may be part of the coiled tubing string 30, in accordance with other embodiments of the invention.

Depending on the particular embodiment of the invention, a one piece connector assembly or a two piece connector assembly (as depicted in FIG. 1) may be used to selectively connect two coiled tubing segments together. For example, referring to FIG. 3, a single piece coiled tubing connector 210 constructed in accordance with an embodiment of the invention may be used to connect a first section of coiled tubing 212 and a second section of coiled tubing 214. The connector 210, having a body 216 having a longitudinal bore 218 therethrough, includes a stiff section 227 and at least one end section 228. Often stiff section 227 is provided between two end sections 228, as is shown FIG. 3. In some embodiments, body 216 of connector 210 may be discontinuous, and in further embodiments, stiff section 227 is separable from one or more end sections 228. In some embodiments of the invention, the body 216 of the connector 210 may be a continuous body in which one region of connector body 216 is stiff section 227 and other region or regions of connector body 216 are end section or sections 228.

The stiff section 227 of connector 210 has an outer diameter that it will fits snugly within the inner diameter of first and second sections of coiled tubing 212 and 214. The exterior diameter of body 216 remains essentially constant throughout stiff section 227, excepting in localized areas where a means, such as a groove or indentation, to effect a connection with coiled tubing 212 and 214 are present.

In end sections 228 of body 216, external diameter 229 of body 216 gradually decreases from the end 231 of the end section 228 proximate to the stiff section 227 towards the distal end 233 of the body 216, such that the external diameter of end section 228 of body 216 is not engaged snugly within the interior diameter of coiled tubing 212 or 214. When coiled tubing 212 and 214 is straight, end section 228 is not in contact with the inner diameter of the coiled tubing 212 or 214 owing to the decreasing external diameter 229 of end section 228. This decreasing external diameter, referred to herein as tapered, may be constructed in any variety of ways that provides a smaller external diameter at the distal end 233 of end section 228; examples of ways by which a taper may be formed include but are not limited to a single angle, a series of short angle sectors, a constant radius, or a compound radius.

As coiled tubing 212 is connected to connector 210 in stiff section 227 and coiled tubing 212 bends as is routine in coiled tubing deployment and operation, only a limited area of end section 228 will be in contact with the interior diameter of coiled tubing 212 as it bends owing to the decreasing exterior diameter 229 of end section 228. In this way, there is a limited area of contact between coiled tubing 212/214 as it bends over the length of end section 228 and that limited area of contact translates along the length of end section 228 as coiled tubing 212 bends. As such, the stress point occurring at the point of contact translates along the end section 228 and overlapping coiled tubing 212, thereby avoiding the formation of a specific point of stress concentration or hinge point. This characteristic is referred to herein as the restrictive bend feature.

The restrictive bend feature avoids the formation of a hinge point resulting from stress repeatedly concentrating in areas. It is known that such hinge points create a weak point in coiled tubing connectors. By design, this restrictive bend feature provides a transition between the stiff section 227 of connector 10 and the coiled tubing 212 or 214 and distributes the strain in the coiled tubing over the length of end section 228 rather than in a localized hinge point. By such a strain distribution, the maximum stress imposed on any particular point of coiled tubing 212 or 214 overlapping end section 228 and the duration of time at which any particular point is subjected to that stress is reduced. This serves to improve the low cycle fatigue performance of the overall coiled tubing and connector configuration. Such a configuration is notably different from known flexible internal connectors and is counter to the conventional approach of providing a flexible middle section with stiffer section on either side. Thus the coiled tubing connector may be useful to provide a connection that is flexible on both ends and stiff in the middle.

In various embodiments, the diameter of the internal surface of body 216 along longitudinal bore 218 in end section 228 may decrease in a similar manner to external diameter 229, may remain the same throughout end section 228, or may increase to form an internal tapered surface 230. In embodiments in which the diameter of the internal surface of body 216 along longitudinal bore 218 in end section 228 remains the same or increases, the cross sectional wall thickness of body 216 in end section 228 decreases toward distal end 233 as a result of decreasing external diameter 229. This decreasing wall thickness makes end section 228 more flexible at distal end 233 and increasingly less flexible along the length of end section 228 extending to the end of stiff section 227. In this way, connector 210 is most flexible at the distal end 233 of end section 228 and has diminishing flexibility traversing toward stiff section 227 along the length of end section 228 such that the stiffest area of end section 228 is at end 231 adjacent to stiff section 227.

Connector 210 may be secured to the coiled tubing 212 and 214 in stiff section 227 by techniques suitable for use with internal connectors such as roll-on connectors, screws, crimping, and dimpling. In FIG. 3, the connection between stiff section 227 and coiled tubing 212 and 214 is shown made by indentations 222 on the outer surface of stiff section 227 receiving protuberances 220 on the coiled tubing 212 and 214. Such indentations may be made a variety of ways such as surrounding the coiled tubing with a mold and pressing the mold to form indentations, using a push or screw to form the indentations, or using a pre-pattern of weaker points in stiff section 227 into which coiled tubing 212 or 214 may be easily pressed. In some embodiments, the exterior surface of stiff section 227 may be patterned in a manner to facilitate this connection with coiled tubing 212 and 214. For example, indentations in the exterior surface of stiff section 227 may spread uniformly about the circumference in a localized area or along the length of stiff section 227. Alternatively, depressions for receiving screws holes may be provided in the exterior surface of stiff section 227; such depressions may similarly be in a localized area or along the length of stiff section 227.

In addition, the pattern, shape, or depth of such indentations may be varied and in particular, be varied in such a manner that the stress during bending of the connection is distributed across the indentations and not concentrated in a limited localized area. Moreover this variation may be done in such a manner as to vary the relative snugness of the connection between connector 210 and coiled tubing 212 or 214 across stiff section 227 of connector 10 such that the connection between connector 210 and coiled tubing 212 or 214 is relatively snug near the ends of coiled tubing 212 or 214 and the connection is less snug in other areas of stiff section 227 of connector 210. For example, dimple screws closest to the ends of coiled tubing 212 or 214 of the tubing can be tightened to a different depth compared to those screws furthest from the ends of coiled tubing 212 or 214.

Alternatively or in addition to indentations along the external surface of stiff section 227, indentations may be provided on the internal surface of body 216 along longitudinal bore 218. In this manner, a thinner wall section of body 216 is provided in desired locations at which coiled tubing 212 or 214 may be pressed or crimped to secure contact between connector 210 and coiled tubing 212 or 214. In another embodiment, a groove may be provided around the circumference of stiff section 227 or a series of circumferential or partially circumferential grooves may be placed or staggered along the length of stiff section 227. Various combinations of these techniques may also be used and are considered within the scope of the present invention.

Connector 210 may preferably be provided with one or more seals 224 to prevent fluid leakage between the connector 210 and each of either or both of the coiled tubing 212/214. These seals 224 may be of any known type, including but not limited to O-rings, chevron seals, T-seals, dynamic seals such as PolyPak™, and various other elastomeric devices.

In some embodiments of the invention, the connector 210 may include an annular lip 226 disposed about the body 216 in the stiff section 227 and positioned such that it is disposed between the respective ends of the coiled tubings 212 and 214. The diameter of annular lip 226 is the same or essentially equivalent to the outer diameter of coiled tubing 212 and 214. As such, annular lip 226 does not preclude connector 10 from passing through the wellhead equipment. Annular lip 226 provides support for the end of the coiled tubing 212 or 214 or to reduce forces that cause flaring of tubing ends and also to contain and protect the tubing ends. As will be appreciated by those of skill in this art, the annular lip 226 functions to reduce deformation or “egging” of the ends of the coiled tubing 212 or 214 during use.

In some embodiments, a flow control device, such as a check valve, may be used in conjunction with connector 210. The flow control device permits fluid flow through in one configuration and restricts fluid flow through in another configuration. Methods of switching such flow control devices from one configuration to another configuration are well known and include, for example, exerting an axial external pressure on the connector, dropping a ball, or providing a control signal. Such embodiments are of particular use when the coiled tubing is under pressure, such as well pressure or fluid pressure. The flow control device may be placed within stiff section 227 of connector 210 (see FIG. 9), within coiled tubing 212 (see FIG. 10) or 214 adjacent to connector 210 (see FIG. 10). A combination of internal and external flow control devices may be also used.

In some embodiments of the invention, the connector 210 is utilized to connect coiled tubing 212 and 214 of different wall thicknesses and correspondingly different bending stiffnesses, advantageously eliminating the need to weld the coiled tubing sections having different wall thicknesses. For example, coiled tubing 212 has a wall thickness different than the wall thickness of coiled tubing 214. The wall thickness of coiled tubing 212 may be greater than the wall thickness of coiled tubing 214 or the wall thickness of coiled tubing 214 may be greater than the wall thickness of coiled tubing 212. Alternatively, the coiled tubings 212 and 214 have different wall thicknesses and substantially the same outer diameter. Alternatively, the coiled tubings 212 and 214 have different wall thicknesses only at those portions of the coiled tubings 212 and 214 where the coiled tubings 212 and 214 are joined by the connector 210, such as end portions thereof or the like.

As shown in FIGS. 4A, 4B and 4C, the decreasing exterior diameter 229 of end section 228 can be constructed on the external surface of body 216 in a variety of ways, including but not limited to with a single angle, a series of short angle sectors, a constant radius or a compound radius. In some embodiments, the diameter of the internal surface of body 216 along longitudinal bore 218 may increase in end section 228 to form an internal tapered surface 230. For example, in the specific embodiments shown in FIG. 3, end section 228 is shown having an outer tapered surface 229 and a tapered internal surface 230 in longitudinal bore 218. This internal tapered surface 230 similarly may be constructed in a variety of ways, including but not limited to with a single angle, a series of short angle sectors, a constant radius, or a compound radius. In some embodiments, the manner in which decreasing exterior diameter 229 and internal tapered surface 230 are constructed may be the same and in some embodiments, the manner in which they are formed may be different. In the specific embodiment shown in FIG. 4A, end section 228 includes an internal tapered surface 230 and a tapered outer surface of body 229. In the embodiment shown in FIG. 4B, end section 228 includes a plurality of outer tapered surfaces, or short angle sectors, 229A, 229B and 229C, and internal surface 230 is not tapered. In the embodiment shown in FIG. 4C, end section 228 includes a tapered outer surface 229 formed by a constant radius and internal surface 230 in the longitudinal bore 218 is not tapered.

There is shown in FIG. 5 a coiled tubing connector 210 constructed in accordance with the present invention and in use to connect a first section of coiled tubing 212 and a tool string 213. Connector 210 has a body 216 having a longitudinal bore 218 therethrough and comprises a stiff section 227 and an end section 228. In some embodiments, connector 210 may disassembled by separating stiff section 227 may be separated from end section 228 and assembled by attached stiff section 227 to end section 228 by using any number of connection methods known for connecting while maintaining a flush exterior surface such as threading, patterned jointing, or lock and key.

Stiff section 227 of connector 210 has an outer diameter that fits snugly within the inner diameter of coiled tubing 212. The other end 241 of stiff section 227 connects to tool string 213. Such a connection to tool string 13 may be made by any number of connection methods known for connecting while maintaining a flush exterior surface such as threading, patterned jointing, or lock and key. In end section 228, the external diameter 229 of body 216 gradually decreases from end of the end section 228 proximate to the stiff section 227 towards the distal end 233 of the body 216, such that the external diameter 229 of end section 228 at the distal end 233 of body 216 is not engaged snuggly within the interior diameter of coiled tubing 212. When coiled tubing 12 is straight, end section 228 is not in contact with the inner diameter of the coiled tubing owing to its decreasing external diameter 229. In this way, there is a limited area of contact between coiled tubing 212/214 as it bends over the length of end section 228 and that limited area of contact translates along the length of end section 228 as coiled tubing 212 bends. As such, the stress point occurring at the point of contact translates along the end section 228 and overlapping coiled tubing 212, thereby avoiding the formation of a specific point of stress concentration or hinge point. The restrictive bend feature of end section 228 previously described is present in the embodiment shown in FIG. 5.

A specific embodiment is shown in FIG. 6 in which two coiled tubing connectors 210 constructed in accord with the present invention are shown to connect a first section of coiled tubing 212, a tool string 213, and a second section of coiled tubing 214. Each coiled tubing connector 210 has a body 216 having a longitudinal bore 218 therethrough and comprises a stiff section 227 and an end section 228. Each tubing connector 210 is connected to coiled tubing 212 or 214 at stiff section 227 and to tool string 213 at one end 241. The first tubing connector 210 is connected at stiff section 227 to coiled tubing 212 and the second tubing connector 210 likewise is connected at stiff section 227 to coiled tubing 214. Stiff sections 227 have an outer diameter that fits snugly within the inner diameter of coiled tubing 212. End section 228 of each of the first and the second tubing connector 210 has an external diameter 229 that gradually decreases from the end 240 of the end section 228 proximate to the stiff section 227 towards the distal end 233 of the body 216, such that the external diameter 229 of end section 228 at the distal end 233 of body 216 is not engaged within the interior diameter of coiled tubing 212 or 214 respectively when the coiled tubing is not bent.

In some embodiments, first or second connector 210, or both, may comprise a body 216 in which one region of the body 216 is stiff section 227 and another region of body 216 is end section 228. In other embodiments, body 216 of the first or second connector 210, or both, may disassembled by separating stiff section 227 from end section 228 and assembled by attached stiff section 227 to end section 228 using any number of connection methods known for connecting while maintaining a flush exterior surface such as threading, patterned jointing.

Stiff section 227 of each the first and second connectors 210 have an outer diameter that fits snugly within respectively the inner diameter of coiled tubing 212 or 214. End section 228 of each of the first and the second tubing connector 210 has an external diameter 229 that gradually decreases from the end 231 of the end section 228 proximate to the stiff section 227 towards the distal end 233 of the body 216, such that the external diameter 229 of end section 228 at the distal end 233 of body 216 is not engaged within the interior diameter of coiled tubing 212 or 214 respectively when the coiled tubing is not bent. This restrictive bend feature of end section 228 previously described is included in the embodiment shown in FIG. 6.

Each of the embodiments described has a reduction in the exterior diameter of end section 228. When bending occurs in routine use, coiled tubing 212/214 bends until it contacts end section 228. As bending continues, the contact point between coiled tubing 212/214 and end section 228 translates along the length of end section 228, thereby avoiding a localized hinge point. In this way, connector 210 of the present invention undergoes lower strain during bending and as a result, suffers lower fatigue and has a longer useful life.

Advantages of the connector described herein may be seen by referring to FIGS. 7A and 7B in which output from finite element modeling is shown. FIG. 7A illustrates the output of finite element modeling of a known internal coiled tubing connector having a flexible center section and stiff end sections; numerous areas of high strain concentration 250 are shown including an extended area of high strain concentration 250 in the flexible center section. FIG. 7B illustrates the output of finite element modeling having the same inputs as FIG. 7B, except that the connector is modeled is of the present invention; few areas of high strain concentration 250 are shown for the present invention connector. As high strain concentration leads to diminished usage life or to greater risk of failure, the advantages of the connector described herein are apparent from a comparison of FIG. 7B to FIG. 7A from which is can be seen that connector 210 of the present invention undergoes less strain than the coiled tubing connector having a flexible center section.

As shown in FIG. 8, in another specific embodiment, connector 210 may further be provided with a flow guide/debris barrier 232 disposed at each end of the connector 210. The barrier 232 may include a body 234 with a tubular section 236 extending therefrom and adapted to fit within the bore 218 of the connector 210. The body 234 may include a shoulder 238 designed to engage the tip of end section 228 of connector 210. Body 234 may include an annular recess 244 for receiving an annular seal 242. The body 234 may further include a tapered inner bore 240. The debris barrier 32 functions to keep debris and solids, which could impede controlled bending, out of the restrictive bend area between external diameter 229 of end sections 228 and internal surface 230 of the coiled tubings 212/214. Barrier 232 may be separate from the connector 210, as shown, or it may be integral with the connector 210. In various embodiments, barrier 232 may be rigid or flexible. An example of an integral flexible embodiment is an elastomeric cone molded to the end of connector 210. Any combination of these techniques may be used. If barrier 232 is separate from connector 210 instead of integral with it, it may be held in position by a coiled tubing weld bead 246 on one side and connector 210 on the other side. FIG. 8 further illustrates that connector 210 may include an anti-extrusion ring 248 adjacent seal 224.

Advantages of the connectors in accordance with embodiments of the invention include a tensile strength similar to the tensile strength of the coiled tubing; the capability of bending around a coiled tubing reel and an injector gooseneck during operation; a low cycle fatigue life similar to the coiled tubing; a pressure tight seal both from internal and external sources; and the ability to pass through a wellhead assembly.

In some embodiments, a flow control device, such as a check valve, may be used in conjunction with connector 210. The flow control device permits fluid flow through in one configuration and restricts fluid flow through in another configuration. Methods of switching such flow control devices from one configuration to another configuration are well known and include, for example, exerting an axial external pressure on the connector, dropping a ball, or providing a control signal. Such embodiments are of particular use when the coiled tubing is under pressure, such as well pressure or fluid pressure. The flow control device 260 may be placed within stiff section 227 (FIG. 9) of connector 210 or within coiled tubing 212 (FIG. 10) or 214 (FIG. 11) adjacent to connector 210. A combination of internal and external flow control devices may be also used.

FIG. 12 depicts an embodiment of a two piece connector assembly for joining two coiled tubing segments together, in accordance with other embodiments of the invention. The two piece connector assembly includes a first connector 400 (an embodiment of the connector 70 of FIG. 1, for example), which mates with another connector 410 (an embodiment of the connector 80 of FIG. 1, for example). In some embodiments of the invention, each coiled tubing segment is transported to the well site with the connectors 400 and 410 (one secured to each end) already being in place on their respective coiled tubing segments.

Each connector 400, 410 has the same general design, with an end connector distinguishing one connector 400, 410 from the other. For example, in accordance with some embodiments of the invention, the connector 400 is a female connector due to a female end connector 350 that mates with a male end connector 354 of the connector 410. The opposite ends of the connectors 400 and 408 receive the respective coiled tubing sections 330 a and 330 b, respectively. Each end connector 350, 354 is a non-rotating connector and may be one of numerous different types of connectors, depending on the particular embodiment of the invention. For example, in accordance with some embodiments of the invention, the end connectors 350 and 354 may be threaded connectors, and in other embodiments of the invention, as another non-limiting example, each end connector 350, 354 may be a crimp-type connector. Thus, many variations are contemplated and are within the scope of the appended claims.

As depicted in FIG. 12, the connector 400 has a generally tapered exterior end surface 371, which is inserted into the end of the coiled tubing section 330 a. The surface 371 establishes a sliding area of contact between the connector 400 and the coiled tubing section 330 a, to prevent a hinge point. Between the surface 371 and the end connector 350, the connector 400 may include a profile for purposes of attaching the coiled tubing section 330 a to a connector body 373. As an example, as depicted in FIG. 3, in accordance with some embodiments of the invention, the connector body 373 includes indentations 360 which receive corresponding protuberances 370 of the coiled tubing section 330 a when the coiled tubing section 330 a is crimped into the connector body 373.

Apart from having the opposite-type end connector 354, the connector 410 has a similar design to the connector 400, in accordance with some embodiments of the invention. In this regard, as shown in FIG. 3, the connector 410 includes a connector body 383, which has a tapered end surface 381 that is received into the coiled tubing section 330 b. Furthermore, the connector body 383 has indentations 380 that receive corresponding protuberances 382 when the coiled tubing section 330 b is crimped into the connector body 383.

In accordance with some embodiments of the invention, a check valve may be disposed in one or both of the connectors 400 and 410 for purposes of maintaining fluid seal integrity of the coiled tubing string 330. In this regard, it is possible that during its lifetime, the coiled tubing string 30 (see FIG. 1) may possibly develop a pin hole leak beneath the well tree 31. This leak, in turn, may cause the communication of well fluid from the annulus into the central passageway of the coiled tubing string 30, thereby compromising the seal integrity of the well. As depicted in FIG. 3, in some embodiments of the invention, a flow control device, such as a check valve 390, may be located in the connector 410 (i.e., the bottom connector), although the check valve may be located in the upper connector 400, in accordance with some embodiments of the invention. A particular advantage of incorporating a flow control device, such as the check valve 390, into the bottom connector 410 is that when the connectors 400 and 410 are separated at the slips 56 (see FIG. 1), a seal is maintained on the central passageway of the coiled tubing string 30. Additionally, should a leak develop, additional measures may be employed using the one-way communication path through the check valve 390, such as injecting a kill fluid through the check valve 390 and into the central passageway of the deployed coiled tubing string, for example.

While the present invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention. 

1. A method usable with a well, comprising: changing a connection between a first coiled tubing segment and a second coiled tubing segment while an upper portion of the first coiled tubing segment is out of the well and the remainder of the first coiled tubing segment is deployed in the well; and subsequently deploying the upper portion of the first coiled tubing segment into the well or retrieving the remainder of the first coiled tubing segment from the well.
 2. The method of claim 1, further comprising: partially deploying the second coiled tubing segment into the well leaving an upper end of the second coiled tubing segment out of the well; and subsequently connecting a bottom end of a third coiled tubing segment to the upper end of the second coiled tubing segment; and deploying the remainder of the second coiled tubing segment into the well.
 3. The method of claim 1, further comprising: wherein partially deploying the second coiled tubing segment into the well leaving an upper end of the second coiled tubing segment out of the well; and subsequently connecting a bottom end of a tool to the upper end of the second coiled tubing segment; connecting an upper end of the tool to a bottom end of a third coiled tubing segment; and deploying the remainder of the second coiled tubing segment and tool into the well.
 4. The method of claim 1, wherein the first coiled tubing segment has a length less than approximately 5000 feet.
 5. The method of claim 1, wherein the second coiled tubing segment has a length less than approximately 5000 feet.
 6. The method of claim 1, further comprising: engaging the upper end of the first coiled tubing with slips.
 7. The method of claim 1, further comprising: disposing a check valve in a connector attached to the first coiled tubing segment or the second coiled tubing segment.
 8. The method of claim 7, wherein the act of disposing the check valve comprises disposing the check valve in a connector attached to the upper end of the first coiled tubing segment.
 9. The method of claim 1, wherein the first coiled tubing segment and the second coiled tubing segment have different wall thicknesses.
 10. A system usable with a well, comprising: a first coiled tubing segment; a second coiled tubing segment; and slips to secure an upper end of the first coiled tubing segment when the first coiled tubing segment is partially deployed in the well to permit the second coiled tubing segment to be selectively connected to or disconnected from the first coiled tubing segment.
 11. The system of claim 10, further comprising: an injector to deploy the first and second coiled tubing segments in the well or retrieve the first and second coiled tubing segments from the well.
 12. The system of claim 10, further comprising: a third coiled tubing segment, wherein the slips are adapted to engage the second coiled tubing segment to secure an upper end of the second coiled tubing segment such that a bottom end of the third coiled tubing segment may be connected to the upper end of the second coiled tubing segment.
 13. The system of claim 10, wherein the first coiled tubing segment has a length less than approximately 5000 feet.
 14. The system of claim 13, wherein the second coiled tubing segment has a length less than approximately 5000 feet.
 15. The system of claim 10, further comprising: a check valve disposed in the first coiled tubing segment or the second coiled tubing segment.
 16. The system of claim 10, wherein the first coiled tubing segment has a different wall thickness than the second coiled tubing segment.
 17. A method of deploying coiled tubing in a wellbore, comprising: providing a coiled tubing connector having a body with a longitudinal bore therethrough, the body having a first end section and a second end section sections, each end section having a tapered external surface, and a stiff section disposed between the first and the second end sections; disposing the first end section within a first coiled tubing, the first coiled tubing having at least an end portion having a first wall thickness; disposing the second end section within a second coiled tubing, the second coiled tubing having at least an end portion having a second wall thickness different than the first wall thickness; securing the stiff section to the inner diameter of each of the first and second coiled tubings, thereby forming a connected tubing; and lowering the connected tubing into a wellbore. 